\documentclass[]{ctexbeamer}
\usetheme{sjtubeamer}
\tikzfading[name=fade cover,
  left color=transparent!20,
  right color=transparent!20
]
\setbeamertemplate{background}{
\bgcenterbox{
\begin{tikzpicture}
\stamparray{16pt}{(0,0)}
{(\paperwidth,\paperheight)}
\fill[white, path fading=fade cover]
  (0,0) rectangle (\paperwidth,\paperheight);
\end{tikzpicture}
}
}
\begin{document}
\begin{frame}
  背景采用了印记矩阵的设计。
\end{frame}
\end{document}